Microwave switch

ABSTRACT

The invention is directed to a microwave switch comprising a switch housing having side walls in which wave guide terminals are provided, and a switch rotor carried by a shaft which is mounted in bearings in said switch housing and being rotatable between switch positions defined by stop means limiting the rotation of said switch rotor a maximum of 180°, and an electromagnetic driving device having a permanent magnetic rotor part fixed directly onto the shaft of the switch rotor and having diametrically positioned magnetic poles of opposite polarities, and a stator part having an electric driving coil arranged on a magnetic yoke which is connected with two poles shoes, said stop means comprising a stop element on said switch rotor and impact elements provided in said switch housing.

BACKGROUND OF THE INVENTION

One frequent design in prior art microwave switches is such that themicrowave function in itself, that is mainly the switch housing and theswitch rotor and the driving function, that is said electromagneticdriving device or corresponding means for rotating the switch rotor, arebuilt in the form of substantially separate units. Generally, thesedriving devices comprises a magnetic rotor element which is surroundedby at least one electromagnetic stator element, being each optionallyprovided with one or several driving coils generating a magnetic fieldfor driving the rotor element. Such designs are disclosed in U.S. Pat.Nos. 3,694,782, 4,227,164, 3,761,851 and 4,500,861. In order to obtain areduced switching time strong electromagnets are frequently usedrequiring a high electrical power and having a big soft iron mass.Frequently used are also arrangements of several electromagnets beingactivated simultaneously for generating a stronger magnetic field. As aconsequence the driving devices are characterized by a complicateddesign including several mechanical and electrical elements, high weightand a comparatively large volume, being thereby space demanding in theactual applications.

The rotary movement of the driving device may be transferred to theswitch rotor in different ways. For example, U.S. Pat. No. 4,795,929discloses a construction using an arm 50 (FIG. 4) which is attached ontothe shaft 20 of the driving device. The movement of said shaft in itsturn is transferred to the microwave switch rotor by a type ofmechanical gear, which may comprise so called "Maltese cross" by whichsaid arm is mechanically connected with the switch rotor. Theconstruction provides for damping of the rotor movement at the switchpositions. Alternative examples of a movement transmission between thedriving device and the switch rotor are found in U.S. Pat. No.4,520,331.

The comparatively complicated structure of these prior art drivingdevices at the same time ends up in high manufacturing costs for thecomplete microwave switch. Furthermore the prior art constructionscomprise a number of wear suffering detail elements, for example saidmechanical gear, said stop means for defining the switch positions andmechanically controlled switches for the current supply to the drivingcoils, all together reducing the useful life time of the microwaveswitch and causing maintenance costs.

The tendency of a rebounding action between said stop means at theswitch positions is a general problem in microwave switches of the typein question. The problem is enhanced by the fact that a fast switchaction is demanded at the same time by the switch rotor between theswitch positions. The impact energy at the switch positions will alsocause mechanical wear of the stop means.

In U.S. Pat. No. 4,665,373 is disclosed a microwave switch, which, forsolving the problem with said rebounding action, has been provided witha rotatable metal disc of substantially the same weight as the switchrotor. Immediately before the switch position is reached by the switchrotor an impact takes place between corresponding pins on said rotatabledisc and one the switch rotor, thereby transferring the kinetic energyto said disc. As such this design is relatively complicated because therotor is mounted in bearings in the switch housing, being spacedemanding as well. By the mode of operation it is required that themoveable disc in its turn must be stopped and brought to a defined startposition before a nextcoming switch movement.

OBJECTS OF THE INVENTION

The object of the invention is to provide a microwave switch of the typementioned in the introduction and not having the mentioned drawbacks ofprior art, allowing for damping of the switch rotor movement at theswitch positions by simple measures, and allowing for a compactly builtswitch of low weight.

One further object of invention is to use a low number of moving parts,demanding a minimal amount of maintenance, and to provide a switchdesign facilitating correct balancing of component parts and beingtherefore suitable for use in environments exposed to vibrations, forexample in airplanes.

The object of invention is obtained by a microwave switch of the typementioned in the introduction, which is characterized by said stop meanscomprising a shock absorbing disc resiliently arranged in said switchhousing, said disc comprising in one unit said impact elements, definingtogether with said stop element the angle of rotation of the switchrotor, and said impact elements and said disc being symmetricallyarranged in relation to said shaft, said disc performing thereby adamping movement in different directions at the impact of said stopelement against said respective impact elements. By said resilientarrangement of the disc a shock absorbing function is obtained whichprovides for a rapid and effective damping of the switch rotor movementand reducing at the same time the load on said stop and impact elements.

According to the invention said resiliency may preferably be obtained intwo different ways, that is on one hand according to a first embodimentin which said disc is attached to the switch housing by means of a layerof an elastic material, and on the second hand by a second embodiment inwhich said disc has a frictional engagement with the switch housing andmay be displaced between two positions.

In order to save space and weight the driving device of the microwaveswitch according to the invention comprises one driving coil. Whenswitching the switch device the driving current through the coil isreversed by means of an electronic control circuit. According to onepreferred embodiment of the microwave switch according to the inventionsaid electronic control circuit comprises a time function maintainingthe switching current during an elapse of time which is longer than thetime of movement of the switch rotor between the switch positions.Thereby is generated, during a given tie interval after the impact time,a holding force participating to an improved shock absorbing action ofthe disc. The advantage of a purely time based control of this type isthat the time function may be integrated in to the electronic controlcircuit by means of simple programming measures without significantcosts. Another advantage of the purely time based control of theswitching current is the security of current switching, eliminating therisk of over-heating the driving coil of the driving device.

SU 1653036-A (Maksimov A I) discloses a microwave switch in which adelayed interruption of the switching current is obtained byelectromechanical means. The delay is based on the movement of theswitch rotor and means that the movement of a so called "dog" iscontinued a given time after impact of the switch rotor. The mechanicalconstruction is fairly complicated and space demanding. At a malfunctionthe current is not interrupted with a consequent risk of driving devicedamages.

Further features of the microwave switch according to the invention areevident from the succeeding claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described more closely in the following inconnection with a non-limitative embodiment by reference to thedrawings, in which:

FIG. 1 discloses a partly broken up perspective view of a microwaveswitch according to the invention,

FIG. 2 discloses a block diagram showing the structure of the microwaveswitch electronic circuit,

FIG. 3 discloses a detailed view of the attachment of the shockabsorbing disc,

FIG. 4 discloses FIG. 3 in an elevational view of the switch devicehousing with the roof wall thereof eliminated, and

FIG. 5 discloses an alternative embodiment of the shocking absorbingdisc according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The microwave switch as shown in FIG. 1 comprises a switch housing 1having waveguide terminals 2 to which rectangular waveguides may beconnected in the embodiment, as shown. A switch rotor 3 is rotatablymounted on a shaft 4, said rotor being provided with usual ports 2'through which said terminals 2 may be interconnected dependent on theangular position of the switch rotor. The shaft 4 is mounted on bearingsat its upper and lower ends at the roof and the bottom of the switchhousing, respectively, in a professional manner, for example by means ofa ballbearing below rotor 3 at the bottom of the cavity and aballbearing 21 provided on the upper side of the cavity roof asdisclosed in FIG. 3.

The electromagnetic driving device of the microwave switch is integratedwith the upper part of the switch housing. The permanent magnetic rotorpart of the driving device has the shape of a circular rotor disc 5having diametrically positioned magnetical poles N, S of oppositepolarity. The center of said disc is fixed directly onto the switchrotor shaft 4.

The stator part of the driving device comprises a magnetic yoke 6 havingthe shape of an upside down U on which a driving coil 7 is provided. Thelegs of the magnetic yoke transform into a respective disc shaped poleshoe 11 and 12, being arranged in plane with the roof of the switchhousing. In the disclosed embodiment the magnetic yoke and pole shoesare manufactured in one piece of a bent, soft magnetical sheet metal,and consequently the magnetic yoke and the pole shoes have one and thesame thickness. This design of the magnetic yoke and the pole shoesfacilitates manufacturing and reduces costs therefor and at the sametime simplifies mounting on the switch housing.

The poles 11, 12 are provided wit ha respective circle-segment shapedrecess 17, 18, having a shape which adjoins to the circumference of thecircular rotor with an airgap therebetween.

An electronic control circuit 15 is provided for supplying a switchingcurrent to the driving coil of reversible current direction. Theconsequence of a reversible current direction is that one driving coil 7may be used having a single winding instead of two windings according tocommon prior art. At the same time the driving device may be controlledby means of the same set of control signals that are used in traditionaldesigns having two separate windings. This facilitates use of themicrowave switch as a replacement part in existing microwave systems.

The use of one winding means that the full coil space may be used forthis single winding, allowing thereby a 50% reduction of the drivingcurrent and the power consumption in consequence. Alternatively, thevolume and weight of the driving coil may be reduced.

The switch rotor 3 has two switch positions in the disclosed embodiment,being defined by stop means comprising partly impact elements 8, 9arranged on the ceiling of the switch housing 16 by means of an elasticlayer 14, and partly a pin element 10 which is provided on the upperside of switch rotor. The detailed design of the impact elements 8, 9will be described in the following by reference to FIG. 3 and FIG. 4.

Said pin 10 and the impact elements 8, 9 provide a limitation of theswitch rotor rotation angle to a maximum of 180°. In this embodiment theangle of rotation is approximately 90° as is evident from FIG. 4.

The magnetic poles of the rotor disc 5 are arranged with an angularposition in relation to the rotor switch positions, with said pin 10engaging the impact element 8 or the impact element 9, which is suchthat the north pole N and the south pole S, respectively, of the disc ispositioned substantially at the one or the other end of a respectivecircle-segment shaped recess 17 and 18. The magnetic force between thedisc and pole shoes aims to turn said poles towards the respectivecentre of said circle segments. This magnetic force provides a holdingforce at the switch positions, keeping the switch rotor in place alsowithout any current supply to the driving coil 7. The circle-segmentshaped recesses of the pole shoes contribute to stabilization of theswitch positions by increasing the magnetic force between the rotor discand the pole shoes.

The switch rotor shaft 4 is provided with an extension 20 having a gripfor allowing a manual switch-over of the switch rotor between the switchpositions.

A return spring 19 is provided for returning the switch rotor 3 to theposition in which the pin 10 engages the impact element 9 when thecurrent supply to the coil 7 is interrupted. The spring 19 is fittedbetween an arm attached to the rotor shaft and a peg provided in thepole shoe 12. Alternatively, the switch rotor may be returned to saidposition by reversing the current through the driving coil.

The block diagram in FIG. 2 discloses the general structure of theelectronic control circuit 15. The circuit comprises two switchtransistors 23, 24, the respective control inputs of which are connectedto the output of timer circuits 25, 26, respectively. The circuit hasthree inputs A, B and C, the input B being common. These inputscorrespond with the respective inputs of driving devices of atraditional type using two driving coils or windings. Dependent on acontrol voltage which is supplied between terminals A, B and C, Brespectively, a driving current is generated in coil 7 in the one or theother direction through the coil 7.

The current supply is controlled by the switch transistors 23 and 24dependent on the respective timer circuits 25 and 26 by an interruptionof the feed-back conductor of the driving current at a change of stateof the control signal from said respective timer circuits. The timercircuits 25, 26 are so dimensioned that the driving current through thecoil is maintained during an elapse of time which is longer than thetime of movement of the switch rotor 3 between the switch positions. Forexample, the circuits may comprise a clock controlled binary counterwhich counts down a preset time. Alternatively, the delayed interruptionof the current through the coil may be obtained by a capacitor circuitof professional type.

The ability of the control circuit 15 of reversing the driving currentdirection and maintaining the same during said elapse of time are thefunctions which are substantial for the realization of the invention.Remaining constructional details of the control circuit are purelyprofessional and will therefore not be thoroughly described in thiscontext.

FIG. 3 and FIG. 4 disclose more in detail the arrangement of the stopmeans of the microwave switch. In this embodiment the impact elements 8,9 are provided by the ends of a ring-shaped disc 13, being attached tothe ceiling of the switch housing 16. The disc is attached by means of alayer 14 of a shock absorbing elastic material.

The ring-shape of the disc means a comparatively long shock absorbinglength which plays a role for the shock absorbing ability of the disc.The mutual positions of the impact elements 8, 9 are determined by theshape of the disc, which facilitates mounting thereof and adjustment ofthe switching positions.

The disc has a minimum weight with respect to the mass of the switchrotor in order to provide a desirable shock absorption, and at the sametime the stiffness of the elastic material is adapted to the weight ofthe switch rotor. This eliminates the risk of self-oscillations of thedisc in environments exposed to vibrations and the risk that vibrationsof the disc may have an influence on the switch rotor by giving the samean unstable position. When the microwave switch is used in more stableenvironments a disc of substantially the same weight as the switch rotormay be used adequately.

The microwave switch operates in the following manner. In the restposition the magnetic forces aim to rotate the poles of the rotor disc 5towards the centre of the respective circle-segment shaped recesses 17,19 of the pole shoes 11, 12. When a switching current is supplied to thecoil 7 magnetic poles of different polarities are created in the poleshoes 11, 12. If the direction of the current is such that the polarityof the poles shoes corresponds wit the adjoining poles of the rotor disc5 these poles will at first be repelled and rotate the rotor disc 5towards the central position between the pole shoes and thereafterattract the rotor disc against the pole shoes and continuously rotatethe switch rotor until the pin 10 engages the respective impact elements8, 9. By this movement the switch rotor 3 is switched from a first to asecond stable switch position. Thereafter the switching current isinterrupted by the active one of the timer circuits 25 and 26. Switchingto the other switch position is obtained correspondingly by reversingthe direction of the switching current by changing the control signal tothe terminals A, B, C of the control circuit.

FIG. 5 discloses an alternative design 13' of the shock absorbing discaccording the invention as seen from above. The disc is generallyring-shaped and has a central opening 27 and a peripherally arrangedrecess defining said two impact elements 8, 9 and thereby also the angleof rotation of the switch rotor. The disc is fitted for a centralarrangement in relation to the shaft 4 and for attachment in a positionin the switch housing in correspondence with what has been shown in FIG.4. For the attachment in the switch housing the disc is provided withtwo elongated hoes 28, 29 by means of which the disc is fixed by meansof two through-screw joints being preferably spring biased. The springbiasing is such that the disc will be held under pressure against thewall of the switch housing by a force which will provide a desirablefriction between the disc and the wall. Optionally a specificallyselected friction layer may be provided between the disc and the wall.

The elongated holes 28, 29 provide for the desirable resilience of thedisc 13', being thereby movable between two positions defined by thelengths of the holes 28, 29 and said screw joints. When the pin element10 on the switch rotor strikes the impact element 8 the disc 13' ismoved from a first position to a second position, and when the pinelement 10 strikes the impact element 9 at switching the switch rotor inthe other direction the corresponding reverse movement of the disc 13'to its first position takes place. For the control of the movement ofthe disc a bearing pin 30 is provided along a line of symmetry 32through said recess and the center of the rotor shaft. During saidmovement the disc is rotated around the bearing pin. Alternatively, thedisc may be journalled along its internal periphery, for example bymeans of a guiding edge provided around the opening as has beenindicated by the dotted circular line 31.

It is understood that the discs 13, 13' may as well be shapeddifferently maintaining the function thereof. Accordingly said recessfor example may be arranged along the internal periphery of thering-shape or be provided by means of a slot of a corresponding length.

Microwave switches of the actual type have normally two switch position.Of this reason the drawings and the description thereof illustrate anembodiment of this kind. However, it is evident that the switchaccording to the invention may have more than two switch positions,which may be obtained by the provision of adjustable stop means, forexample electromechanically operable vertically adjustable impactelements 8, 9 of a professional type.

I claim:
 1. A microwave switch comprising a switch housing having sidewalls in which wave guide terminals are provided and a switch rotorcarried by a shaft which is mounted on bearings in said housing andbeing rotatable between switch positions defined by stop means limitingthe rotation of the switch rotor to a maximum of 180°, and anelectromagnetic driving device having a permanent magnetic rotor partfixed directly onto the shaft of the switch rotor and havingdiametrically positioned magnetic poles of opposite polarities, and astator part comprising an electric driving coil arranged on a magneticyoke connected with two poles shoes, said stop means comprising a stopelement on said switch rotor and impact elements provided in said switchhousing, characterized bysaid stop means comprising a shock absorbingdisc being resiliently arranged in said switch housing and carrying inone single unit said impact elements defining in combination with saidstop element the angle of rotation of the switch rotor, and said impactelements and said disc being symmetrically arranged in relation to saidshaft, said disc performing thereby a damping movement changingdirections at the impact of said stop element against said respectiveimpact elements.
 2. A microwave switch as claimed in claim 1,characterized bysaid shock absorbing disc being attached to the switchhousing by means of a layer of an elastic material, and said elasticmaterial layer having a stiffness which is adapted to the weight of theswitch rotor so as to suppress rebounds at switching.
 3. A microwaveswitch as claimed in claim 1 or 2, characterized bysaid disc having acomparatively low weight in relation to the switch rotor for suppressingtendencies of self-oscillation of the disc in environments exposed tovibrations.
 4. A microwave switch as claimed in claim 1 or 2,characterized bythe weight of said disc being adapted to the weight ofthe switch rotor for absorbing of shocks therefrom.
 5. A microwaveswitch as claimed in claim 1 or 2, characterized bysaid disc beingmovably attached to the switch housing for a reciprocating movementbetween two positions at the impact of said stop element against saidrespective impact elements, and said disc frictionally engaging theswitch housing.
 6. A microwave switch as claimed in claim 1 or 2characterized bysaid disc being provided with a recess forming saidimpact elements.
 7. A microwave switch as claimed in claim 1 or 2characterized bysaid shock absorbing disc being shaped as a ring, andthe center of said ring coinciding with said switch rotor shaft.
 8. Amicrowave switch as claimed in claim 1 or 2 characterized byanelectronic control circuit having a timer function for supplying aswitch current of reversible current direction to said driving coil,said tier function being arranged to maintain the switch current duringan elapse of time which is longer than the time of movement of theswitch rotor between said switch positions.
 9. A microwave switch asclaimed in claim 1 or 2, said electromagnetic driving device beingprovided on the top of a roof-wall of the switch housing and having itspole shoes resting against the roof-wall and leveled with said permanentmagnetic rotor part being formed by a circular rotor disc, said magneticyoke and said pole shoes being manufactured in one unit from ahomogeneous, soft-magnetic sheet metal of a uniform thickness,characterized bysaid pole shoes being formed by two parallel, elongatedelements in the plane of said roof-wall, the inner long sides in thedirection of said shaft being provided with opposite, circle-segmentshaped recesses adjoining and partly enclosing said rotor disc, and saidmagnetic yoke being shaped as an upside down U, the base of which isformed by a coil carrying element arranged transverse to said pole shoeelements and substantially in a plane which is parallel therewith andthe legs of which are formed by angularly bent leg elements, being eachconnected via an angular bend to a corresponding pole shoe element atone end of its external long side, said leg elements having a lengthwhich is such that a space is formed for the winding of the drivingcoil.
 10. A microwave switch as claimed in claim 1 or 2, characterizedbythe common shaft of the switch rotor and the rotor part of theelectromagnetic driving device being provided with an extensionadjoining the rotor part, said extension forming a grip at the level ofthe upper part of the driving coil for manually switching the switchrotor.